An encoding apparatus down-mixes a multi-channel signal into a signal with fewer channels, and transmits the down-mixed signal to a decoding apparatus. Then, the decoding apparatus restores a multi-channel signal from the down-mixed signal and reproduces the restored multi-channel signal using three or more speakers, for example, 5.1-channel speakers.
Multi-channel signals may be reproduced by 2-channel speakers such as headphones. In this case, in order to make a user feel as if sounds output by 2-channel speakers were reproduced from three or more sound sources, it is necessary to develop three-dimensional (3D) processing techniques capable of encoding or decoding multi-channel signals so that 3D effects can be created.